1. Technical Field
The present invention relates to a heat insulating cooking vessel which may be suitably utilized for a cooking process by which food semi-cooked by heating is kept warm and brought to a completely cooked state.
2. Technical Background
In general, the process of heating and cooking food involves electric heat or a direct flame. However, such a cooking process makes food susceptible to breakdown or scorching due to heating, and consumes a large amount of energy.
A cooking process wherein raw vegetables or grains are immersed in an appropriate quantity of boiling water or a boiling seasoned soup, or semi-cooked food is kept warm for an extended period of time to bring it to a completely cooked state, have been advanced in recent years as processes which resolve the above-mentioned problems.
Conventional heat insulating cooking vessels such as that shown, for example, in Japanese Utility Model 3-10920 (Utility Model Appln., Publication No. Heisei 3-10920), wherein a freely hinged handle is attached at the edge of the mouth of the cooking pot, and an engaging portion is provided to this handle, so that when the handle is operated, the aforesaid engaging portion contacts with a portion of the pot, thereby preventing the food contained therein from easily spilling, are available as heat insulating cooking vessels wherein cooking is performed by placing a cooking pot, containing a food material which has been preheated until semi-cooked, in the heat insulating vessel, closing the vessel to seal it, and maintaining the cooking pot and contents therein in a heat insulating state for a desired period of time.
However, the aforementioned conventional heat insulating cooking vessel has the following problems. Namely, because there is no handle on the heat insulating cooking vessel itself, when carrying it, it is cumbersome to transport. Further, because the secure fit of the lid to the cooking pot cannot be assured, when being carried the cooking pot within the heat insulating vessel shifts easily and the food contained therein spills easily. Moreover, food which has spilled over from the cooking pot into the heat insulating container could spill out from the heat insulating container, presenting a hazard.
A heat insulating cooking apparatus as shown in FIG. 13 is available as a conventional cooking apparatus applicable to this type of cooking. This heating insulating cooking vessel consists of a lid 4 releasably provide to the container 3. The container 3 is closed and sealed with the lid 4 and, moreover, an inner pot 2 is releasably contained in the container 3.
The container 3 consists of an inner bottle 5, which is cylindrical and has a curved bottom, and an outer bottle 6, which has a larger diameter than that of the inner bottle 5 and has approximately the same shape as the inner bottle 5, both bottles being joined airtight at their respective upper edges to form a dual wall structure. The space between the inner bottle 5 and the outer bottle 6 is either a vacuum space or is filled with heat insulating material to form a heat insulating portion 7. A bottom element 8 is disposed on the lower face of the container 3, and container handles 9,9 are attached at both sides of the container 3.
The lid 4 consists of an upper lid element 11 of an approximate disc shape and having a lid handle 10 at its center, and with a lower lid element 12 also of an approximate disc shape, the lower lid element 12 being formed in a unitary fashion with the upper lid element 11. The space between the upper lid element 11 and the lower lid element 12 is filled with heat insulating material.
Next an explanation will be given of the inner pot 2 contained in the heat insulating container 1 with reference being made to FIG. 14. The inner pot 2 consists of an inner pot container 13, an inner pot lid 14 and a grip handle 15. The disk shaped inner pot lid 14, which has a diameter approximately equal to that of the mouth portion of the inner container 13, is placed over the mouth portion of the inner pot container 13 in a freely releasable fashion. Further, both ends of semi-circular arc shaped grip handle 15, which has a diameter approximately equal to that of the mouth portion of inner pot container 13, are attached to stopper portions 16,16, which are provided opposite each other on the outer peripheral wall of inner pot container 13, so that the grip handle 15 can be freely raised or lowered.
In a heat insulating vessel of the aforementioned structure, food contents are placed in the inner container 13, the inner pot lid 14 is closed and inner pot 2 is contained entirely within container 3. By closing the mouth portion of the container 3 with lid 4, the temperature of the contents in inner pot 2 can be maintained over a long period of time, thus obtaining a completely cooked product.
However, conventional heat insulating cooking vessels have the following problems. Namely, because inner pot 2 is placed on the inner face of the bottom of the heat insulating container 1 and a part of the bottom edge of inner pot container 13 is maintained in a state wherein it comes in contact with the edge of the inner face of the bottom of the heat insulating container 1, if the dimensions of the inner bottom surface of the heat insulating container 1 are not highly accurate, i.e., the inner bottom surface of heat insulating container 1 is somewhat distorted or is irregular, then the storage of inner pot 2 in heat insulating container 1 is not stable. Accordingly, in the case where heated food is place in inner pot 2 and hereafter contained in heat insulating container 1, when handling the heat insulating cooking vessel, there is the chance that inner pot 2 will shift or tilt, allowing the contents contained therein to spill out.
Further, due to the impact when the inner pot 2 is placed inside heat insulating container 1, or the vibrations which occur when handling the heat insulating cooking vessel, the contact areas between the bottom edge of the outer surface of the inner pot container 13 and the bottom edge of inner surface of the heat insulating container 1 strike against one another, dents or marks arise in this contact area and in the surrounding vicinity.
Further, because the bottom edge of the outer surface of inner pot container 13 and the bottom edge of the inner surface of the heat insulating container 1 come in contact with one another, heat is easily transmitted from inner pot 2 to the heat insulating container 1, or from the heat insulating container 1 to the inner pot 2 via this contact area, this being problematic in that it gives rise to a reduction in the ability to maintain the temperature.